.300 WSM help

Heres the skinny, I am somewhat new to reloading but have a pretty good grasp of it. In august I am going to Kyrgystan in search of a mid-asian Ibex. My Shots will range anywhere from 200-500 yards so i would like to get proficient to atleast 500 yards. My elevation will be anywhere from 12k-15k feet and temps ranging from 20-80 degrees fahrenheit, with those being extremes.

My problem, I have a Tikka .300 WSM and I did quite a bit of load development over the winter and found a load that performed way above any of my expectations. Problem is this was one of the only loads that performed at all.

This load worked great until the temps started to increase above 70 degrees, with temps above 70 my pressures start to spike. (stiff bolt lift and loose primer pockets). And my POI changes significantly.

Ive done some research on RL-17 and the temp sensitivity seems to be quite common. Ultimately I'd like to stray away from this powder if possible.

It's hard to tell what exactly you've tried with all of your various load combos, but your current load sounds like it's at max pressure. when pressure increases for any reason, you are now over pressure.

I personally think that if 250 yards is your max, do your best to find a 1 moa sweet spot at lower velocity/pressure than you are currently getting with your 180 AB RL17 load. maybe just drop a couple of grains. you should be able to find another sweet spot, and even if it's 100 fps slower it will still have plenty of power for your upcoming hunt.

If you've tried all those other powder and bullet combos and none of them work at any velocity, I would think that there might be something going on with the rifle.

Few thoughts:
H4350 would be a good try. H4350 is not temp sensitive in the range of temps you will be shooting and is very consistent.

Try different primers. Maybe Fed 210m and 215M if you can find them. Some use regular primers with the 300 WSM, but with low side of your temp expectations, I would stay away from them.

Berger 185 and 210 VLDS work well in the 300 WSM try working up a load seating them until they are just touching the lands. They almost always shoot good that way. Hopefully they will still fit in the mag that way, if not, you could single load for long range shots.

Also cutback on the RL-17 load. 66 gr is probably over max for the powder. I just use at most 64 gr of RL-17 with my 300 WSM load with 180 NBT. Try to find a lower node with less powder. Then, if you use a ballistics program, allocate 2 FPS per degree temperature change and see if your ballistics start to line up with the temperature changes. RL-17 is very temp sensitive. I proved that to myself just a few weeks ago.

I actually went to the range yesterday with loads using 1 gr and 2 gr less than previous and the pressure went down but the groups were terrible.

Should I back it off a grain or two and do a seating depth ladder.

It would take forever for me to list the load combos I've tried so far.

If you found a load that shoots good with RL17 and the 180 AB, I do not think you need to repeat all of your other loads. Generally speaking a barrel should have a sweet spot (node) at least every 100 fps. when you are not in a sweet spot, it will throw them all over the place. When you are in the sweet spot, life is good. It looks like dropping 1 to 2 grains is not in a sweet spot.

So your current 66.0 grains shoots great, but is right on the edge of max pressure. you know that 64 and 65 grains do not work. I would probably try 3-shot groups with the following:

61.0
61.5
62.0
62.5
63.0
63.5

Typically a sweet spot will shoot to the same point of impact over about a 1 grain variation (all rifles will vary). Hypothetically, you might find that 62.0, 62.5 and 63.0 all shoot to the same point of impact with very good accuracy... If that were the case I would load all of my hunting loads at 62.5 to be in the middle of that sweet spot. Then if you encounter some temp sensitivity above 70 degrees, you will still be within your sweet spot and same point of impact.

I shot some 175 VLD's and they shot really well when seated just off the lands, but at that depth they are too long for the magazine.

I think there are some Tikka users here that have modified their magazine box to fit longer bullets. not sure on this though... but maybe you could use the search function in the upper right and find some threads on that.